I vote for (c). Even though the Free State Project looks like a long shot, and Seasteading looks like an even longer shot, they are interesting.
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This suggests that the real technological fix for libertarians would be enhanced mobility. By the way, I once heard Robert Metcalfe say that the ultimate killer application for the Internet would be teleporting, so that your physical location is not a constraint. If that were possible, would government rents go way down?

This is exactly right. As evidence, note that capital is more mobile than labor, and gets lower tax rates. If we can increase the mobility of labor, we will decrease tax rates on labor. So while seasteading is a long shot, at least it's pointed in the right direction.

Also, its main obstacles are technological - and humans are damn good at solving engineering problems. I predict that if it doesn't work out, it will be for social or political reasons, not engineering ones.

And that is why I keep saying the PT movement is the avant-garde of libertarianism ;)

You forgot one possibility, though, and that is:
d) government becomes incapable of sustaining such a big size
Developping a distributed (non-centralized) easy to use micropayment system would make this possible. Ripple would be a good contender, IMO.

As has been discussed here in the past (too long ago, since I think it's an interesting topic), what makes the elimination of state power a public good as opposed to a private good may be that if I get rid of the state for myself, then my next door neighbor will also be free of the same state. And, which is more or less the same thing, if I successfully protect my home from an invader then I have successfully protected my neighbor's home as well. But this is the case only because we are geographically tied down by the fact that so much of what we own is fixed in the ground (e.g., our homes, our farms, our buildings). Were everything highly mobile, then protecting oneself against a particular state would become more a private good, because one could simply leave. Should a state decide one day that it wanted to get a piece of a particular company's assets through taxation or nationalization, it would find those assets mysteriously gone. The only way for a state to get a hold of people's wealth then would be by getting them to agree to it; but then the state would no longer be a state but just another private company with suppliers and customers.

Getting back to the current situation, where we have valuable assets that we can't easily keep out of the hands of the state, of course if a state is sufficiently intolerable, then many people will be willing to leave behind even their homes; hence the need to erect barbed wire to keep people from leaving.

Anyway, a path to anarchy may be making the good of getting rid of the state into more of a private good. Should that be achieved, then people can enter anarchy one at a time.

Adding some detail:

I'm just wondering, what if most of the stuff is portable. For example, a lot of some companies' assets are in electronic form. They can be sent across the world with the push of a button. They can also be duplicated. And encrypted.

Suppose some company is conducting operations in Cuba. The Cuban government decides one day that it will nationalize the company's assets. But it can't - turns out the company can only access its assets by entering a key that is not stored on-site. All its data is just so much random garbage without that key. The software used to operate its machines can also be protected this way.

That doesn't protect everything, but it could conceivably protect almost everything, depending on how much value is stored electronically, how much is stored in the material goods (e.g. buildings, air conditioners, etc.).

If a company can protect itself against nationalization, then maybe it can protect itself against other things. It can actually strike a deal with a country, saying, "we'll come in and do business in your country if you do X, Y, and Z and charge us W in taxes", or something like that. Making a deal, and more importantly, being able to enforce that deal, changes the relationship between a company and a country from one of subject to state to one more resembling the relationship of companies with each other.

One of the things any state can do now is nationalize stuff. If a company can physically protect itself against nationalization, then that makes possible something that was impossible before.

There are lots of countries. If people generally can, without difficulty, without loss to themselves, without giving up a lot, move from country to country, then countries start to compete with each other, and they become less like countries and more like companies. We see a little bit of this when we hear about a country trying to attract foreign investment.

And:

How does the government collect income tax? How does the government know what I make and what you make? It doesn't come around to our houses and make us tell it. It finds out through our company, and it also finds out financial stuff about us through our bank (I think).

So it would seem that the state's hold on us, tax-wise (and its tax-wise hold on us is critical because if it lost that hold the the state would disappear for lack of funds - taxation is the lifeblood of the state) is through big institutions. If the state loses its grip on them, then quite possibly the state, which seems to grip us largely through them, may lose its grip on all of us, tax-wise.

Nice post. This is why governments begin first with the "commanding heights" of the economy; most relevant to your post: banks.

This is why they print money instead of depending solely on taxes. If they have a central bank, they don't need to just tax your business, according to the contract you made; they can simply print money and lend it to where they want to direct production (and nobody will refuse the funds), create inflation and devalue your assets; increase your costs and decrease your bottom line. They have just taxed you without your consent.

In addition, their monopoly on force (if they run the police and courts) allows them to steal in other ways; and their control over the other "commanding heights" means they can manage your other inputs, and sneak in other controls.